Salt product



Patented Jan. 23, 1951 TATES PATENT SALT PRODUCT ration of Delaware NoDrawing. Application August 11, 1948, Serial No. 43,776

13 Claims. 1

This invention relates to a hygroscopic salt which will remainfree-flowing and will not cake although kept for long periods undermoist, humid conditions. Hence the inv ntion is particularly applicableto common table salt (sodium chloride), but is advantageous inpractially all cases where it is desired to use sodium chloride or otherhygroscopic salts in fiowable form. For convenience the invention willbe described hereinafter with reference to table salt.

It is common experience that table salt exposed to a humid atmosphereabsorbs moisture rapidly and soon becomes unfit for table use, whetherkept in shakers or other receptacles on the table or in open canisterson the shelf. As its moisture content increases, the salt becom s dampand loses its normal flowability so that it can not be spread ordistributed evenly, in which condition it will also clog shaker openingsand will not shake out at all. If the moisture content is of asufiiciently high level, the salt, on subsequent drying, agglomerat sinto hard lumps or cakes that can be broken up only with greatdifiiculty. Both of these effects are very troublesome and in an eifortto minimize them it is customary among manufacturers to blend (i. e.,mix) a small amount of an inert condit oning agent or filler such astricalcium phosphate with the salt. These agents, in the form of a finepowder, are distributed by bl nding over the suragents have beenproposed for the same purpose,

such as calcium carbonate, magnesium carbonate, silica gel, etc. Suchagents are helpful in maintaining the salt lon er in fiowable condition,but are by no means a satisfactory solution of the problem as shown byeveryday experience.

On the other hand, it has been 'prorosed for the same purpose to blendthe hygroscopic salt with insoluble metal soaps such as metal stearateswhich are water-repellent. However, such soaps have never been used inpractice as far as we are aware. When salt blended therewith is shakenor otherwise spread over the surface of a-. liquid, it tends to float ina layer on the surface 'and-; vigorous agitation is nece sary toeffeet-dispersion. As the salt itself dissolves, the water-repellentsoap particles separate therefrom and collect on the surface of theliquid, .forming an unsightly scum. Also such salt blends tend to ballup when placed in water or like liquid. These objectionable eifects arequite apparent even though the amount of metal soap is reduced to a fewtenths of one per cent of the salt. They become less apparent as theamount of metal soap is further reduced and are perhaps not material atvery low concentrations, but the effectiveness of the soap is reducedcorrespondingly and at such low concentrations the soap provides nosignificant improvement in the flowability and res stance to caking ofthe salt.

One of the objects of the present invention is to provide a salt whichis far superior in flowability and caking resistance to any priorcommercial salt with which we are familiar.

Another object is to eliminate the disadvantages mentioned above whichhave heretofore militated against if not prevented the use of insolublemetal soaps.

Further objects are to accomplish the foregoing results without imairing the flavor or quality of the salt and without unduly increasingits cost.

We have found that the heretofore mentioned objections to the use ofwater-repellent insoluble metal soaps can largely be avoided if the soapis caused to adhere to or coat the salt particles as describedhereinafter. Also the adhering soap is more effective in maintainingflowability and preventing caking of the salt than soap which is merelymixed with or dusted on the salt. On the other hand, the adhering soaprenders the salt particles more difficultly soluble. and if the amountof soap is sufiicient to effect s gnificant improvement in thefiowability and anti-caking properties of the salt, then prolongedstirring is necessary in order to disperse the insoluble soap before thesalt itself Will dissolve. However. we have found that this furtherdifiiculty can be avoided by the use of a surface-active a ent whichassists in dispersing and solubilizing the soap. Thus it is possible touse the treated salt in the normal manner without scum and withoutinconvenience due to slow dissolution.

In using insoluble metal soaps in the above manner, we have observedthat they are somewhat less efiective in maintaining flowabilit'y thanin preventin caking. A small amount of soap appears to repel part of themoisture to the surface of the bed of salt so that if caking shouldoccur on subsequent drying, the cake is restricted to a relat vely thinsurface layer of the bed and can be broken up easily. However, somemoisture is absorbed throughout the mass of salt so that it soon reachesthe moisture levelat which it becomes non-flowable. Hence a relativelylarge amount of soap must be used to produce substantial improvement inflowability whereas as much smaller amount will produce a high degree ofimprovement in anti-caking properties.

0n the other hand, inert conditioning agents such as those mentionedabove are more effective in maintaining fiowability than in preventingcaking, being relatively inefiective in the latter respect as comparedwith insoluble metal soap. Hence we prefer in practice to employ both aninert conditionin agent and an insoluble metal soap in combination. Asthe absorption of moisture by the salt progresses, flowability ismaintained by the conjoint action of these agents a large part of whichis attributable to the inert conditioning agent. Anti-caking propertiesare also contributed by both agents, but the part played by the soap isrelatively much greater and that played by the inert conditioning a entis relatively much less than in the case of flowability. Hence theamount of soap is determined -principally by the degree of improvementin anti-caking properties that is d sired, whereas a high degree ofimprovement in fio ability is obtained at the same time due to thegreater effectiveness of the inert conditioning agent in this respect.This conjoint action thus permits a reduction in the amount of soaprequired and reduces the cost of the final product since such soaps arenormally more expensive than suitable inert conditioning agents.However. it will be understood t at scan and surface-active agent or mixthe soap with the salt and then to heat the mixt re to the softeningpoint of the soap to cause it to adhere to the s lt on cool n For bestresults the soap should be finely divided in the form of an impalnablepowder. Where the above method is not feasible, howev r, other suitablemethods ma be used such as dissolving the soap in a volatile solvent andspraying or otherwise distributing the solution on the salt.

Prolonged working of a dry mixture of salt and soap to achieve aspreading or coating of the soap on the salt also is effective,particularly if the salt is warm.

The amount of soap to be used will depend on the degree of improvementthat is desired in the properties of the salt, on the degree ofeffectiveness of the particular metal soap used. and of course onwhether or not an inert conditioning agent is employed as well as soap.By way of example, particularly effective soaps such as magnesium,calcium, and lithium stearates may be used in very small amounts of theorder of 02-03% by weight of the salt, in combination with inertconditioning agents such as magnesium carbonate in amounts of 2-3% onthe same basis, with the result that the salt remains flowable severaltimes as long as the untreated salt and resists caking even more. Lesseramounts of these soaps and conditioning agent can 19. i fieil,

but at the sacrifice of some of the protection afiorded the salt. As arule it will not be desirable to reduce the amount of soap below about0.05% or the amount of conditioning agent below about 0.25%, because thedegree of improvement in the properties of the salt would then becomeunimportant. Larger amounts of the soap and conditioning agent, on theother hand, provide still greater protection than that mentioned above,but generally it is undesirable for the amount of the combinedingredients to exceed about 5-6% of the salt because solutions of thelatter then tend to become cloudy and turbid. Within this practicallimit, the proportions of soap and conditioning agent may vary. Both maybe increased more or less proportionately to say O.5-1% soap and 4.5 5%conditioning agent, or one only may be increased as for example in thecase of 0.2-0.3% soap and 5% conditioning agent, etc.

The amounts of other soaps to be used will differ somewhat from theamount of magnesium stearate for the same degree of improvement in theproperties of the salt. Calcium and lithium stearates, for example, arepractically as effective as magnesium stearate and can be used inapproximately the same amounts whereas aluminum stearate is lesseffective and must therefore be employed in greater amounts. The amountof soap required may also be influenced to some extent by the use ofconditioning agents other than magnesium carbonate as describedhereinafter.

If no inert conditioning agent is used, on the other hand, the amount ofsoap needs to be largely increased if substantial improvement inflowability is to be effected. With magnesium stearate, for example, theamount of soap needs to be increased to about 2% to effect as muchimprovement in flowability as the combination of only 02-03% magnesiumstearate plus 2% magnesium carbonate. However, the cost of suchincreased amount of soap is several times that of the much smalleramount of soap plus the conditioning agent. Hence it is not desirable asa general rule to use soap without conditioning agent, the conjoint useof less soa-p together with a conditionin agent being preferred becauseof greatly reduced cost.

Generally speaking, the inert conditioning agent may be of any suitablekind such as those mentioned above, but we have found that such agentsvary in effectiveness. bonate is one of the most effective conditioningagents and in practice we prefer to employ about 2% magnesium carbonateby weight of the salt. As the amount of magnesium carbonate isdecreased, flowability is lost at lower moisture levels and thereforemore quickly, and below about 0.25% the conditioning effect of themagnesium carbonate becomes unimportant from the practical standpoint.On the other hand, the amount of magnesium carbonate can besubstantially increased up to 4.5% for prolonged flowability as notedabove.

Similar variations may occur in the amounts of other conditioning agentswhich in general are less effective than magnesium carbonate. Forexample, nearly twice as much tri-calcium phosphate is required tomaintain flowability to the same extent as with magnesium carbonate.Fence within the practical up er limit of around 5% conditioning ag nt mntioned above, substant a improvement in fiowabi ity can be effectedwith conditioning agents other than mag- Magnesium cari nesiumcarbonate, but the latter is more effective at much lowerconcentrations.

Any suitable method may be employed for adding the conditioning agent tothe salt. However, these agents being in the form of dry dust or powderare preferably simply mixed thoroughly with the salt by stirring or thelike.

The primary requirement for the surface-acting agent in all cases is theability to aid in the wetting and dispersion of the soap. However, intable salt the surface-active agent should preferably impart noobjectional flavor to the salt or to products seasoned therewith, andshould not produce toxic or otherwise objectionable thermaldecomposition products when subjected to maximum cooking temperatures,say 500 F.-600 F. These requirements lead to the following types andclasses of surface-active agents:

I. Anionic agents of the class of sulphonated amides III. Non-ionic amplthe commercial products iglhigon X100 and Triton 2. Polyalkylenederivatives of hexitol anhydride fatty acid esters such aspolyoxyethvlene sorbitan monolaurate and the commercial products AtlasG7596B and ,Atlas G7596C. for example.

The surface-active agent can be applied to the aryl polyether alcohols,for .ex-

salt in any suitable manner, whereby it is distributed with reasonableuniformity throughout the mass of salt. For example, it can be dissolvedin a suitable solvent which is distributed over the salt and the solventthen allowed to evaporate. The surface-active agent can also be absorbedon the conditioning agent, when used, and the mixture then blended withthe salt, but in such cases an excess amount of surface-active agent isdesirable because some of the agent may not be released for action indispersing the soap. The preferred method, however, is to mix thesurface-active agent with a small quantity of salt which mixture is thenblended with a larger quantity of salt to obtain the desireddistribution of the surface-active agent. For example, Hyamine 1622, asolid, can be mixed thoroughly in finely divided form with a smallquantity of salt, providing a mixture which can be blended convenientlywith the major portion of the salt. Similarly polyethylene glycol 600distearate, which is a waxy solid, can be ground with a small quantityof salt, and polyoxyethylene sorbitan monolaurate, which is a viscousliquid, can be mixed thoroughly with a small quantity of salt, toprovide mixtures for subsequent blending with the major portion of thesalt.

The amount of surface-active agent to be used depends in the firstinstance on the wetting and solubilizing capacity of the particularagent employed and on the rapidity with which the salt is desired todisperse and pass into solution, but the effect of the agent on the drymixture of salt is also a factor. If the amount of surface-active agentis too small the salt will be difiicult to disperse and dissolve. If theamount of surfaceactive agent is too large the salt will disperse anddissolve readily enough but will tend to become damp and non-flowable onexposure. However, this tendency may be counteracted and the advantageof rapid dispersion still obtained by suitable additions of inertconditioning agent.

For most purposes, it will be found desirable to use an amount ofsurface-active agent which will cause the treated salt to disperse anddissolve with a readiness as nearly comparable to that of plain salt aspracticable and yet not become nonfiowable on exposure. However, theremay. be occasions when, in the interest of assuring particularly goodfiowability, a lower degree of dispersibility than otherwise attainablemay be preferred and, conversely, a higher rate of dispersion may attimes be desired at the sacrifice of flowability. Moreover, the presenceor absence of an inert conditioning agent, as well as the soap contentof the salt when no filler is used, will have a bearing on the extent towhich the dispersibility of plain salt can be approximated by additionof a surface-active agent without rendering the treated saltnon-fiowable. Thus, a greater amount of surface-active agent can safelybe used when a conditioning agent is present, and salt having no fillerbut a high soap content will tolerate more of the surface-active agentwithout becoming non-fiowable .than salt having a low soap content. Inany event, the safe upper limit on surface-active agent addition will beabout the same whether the salt contains an appropriate amount ofconditioning agent or its equivalent in the form of a higher proportionof soap.

The actual amount of surface-active agent required in a given case willof course depend on the effectiveness of the particular agent used. Withpolyoxyethylene sorbitan monolaurate and Hyamine 1622, for instance, theaddition of as little as 0.025% by weight of the salt may be sufficientwhen only a small improvement in dispersibility is desired, whereas useof 01-02% will impart a rate of dispersion and dissolution approximatingthat of plain salt but result in a r ion-flowable product unless thesalt is blended with a suitable quantity of conditioning agent or has asoap content of equivalent value. On the other hand, if Igepon T orpolyethylene glycol 600 distearate is used as the surface-active agent,considerably larger amounts may be employed to improve dispersibilitybefore encountering any problem of non-flowability. With them, as muchas 0.5% may safely be incorporated in salt having a low soap content,and as much as 0.75% in' salt containing an added conditioning agent.Similar variations in effectiveness may be expected with othersurface-active agents of the types heretofore named, but in general theproportions in which they will be found useful will fall within thelimits above mentioned.

By way of example, a suitable table salt may be prepared in thefollowing way. Hot salt as it comes from the screens (about 175 F.) isfirst blended with 0.25% finely powdered magnesium stearate, after whichthe temperature of the blend is raised to about C. The stearate softensand melts partially at this temperature, creeping over the surfaces ofthe salt particles and adhering firmly thereto on subsequent cooling. Asmall part of this salt, say 5%, is then mixed with an amount ofpolyoxyethylene sorbitan monolaurate equivalent to 0.15% of the whole,and this mixture is then blended with the remainder of the salt. Finallythe so-treated salt is blended with about 2% magnesium carbonate.

A blend prepared in the above manner was compared with a blend of thesame salt with the same amount of magnesium carbonate only. A quickpractical comparison as to flowability can be made by adding knownvolumes of water to the samples and determining the moisture levels atwhich the salt will no longer shake from shakers. Both samples becamenon-usable at about 1.75% moisture, since the amount of soap was smalland fiowability was maintained principally by the magnesium carbonate.However, the fiowability of the first sample embodying the presentinvention was better as the moisture level approached this limit, asshown by the fact that at 1.25% moisture only 2% of the first sampleremained in the shaker as compared with 28% of the second sample underthe same conditions.

The use of the same amount of soap but of increasing amounts ofmagnesium carbonate up to 5% raised the moisture level at which the saltbecame non-usable to 4.75 When the soap was omitted, the salt plus 5%magnesium carbonate alone became non-usable at 3.5% moisture, the elTectof the soap on fiowability being more evi dent under these conditions.

The effect of the soap on anti-caking properties was much more marked.The second sample (2% MgCO3 ony) was 87% caked in the shaker after beingkept in a bell jar over water for 96 hours and then dried 16 hours at 450., whereas the first sample (including 025% soap) was only about 8%caked after 168 hours exposure and only 45% caked after 240 hoursexposure in the bell jar. Both samples were far superior to theuntreated salt which was 72.5% caked after only 48.5 hours in the belljar.

In the absence of magnesium carbonate, the amount of soap had to beincreased to about 2% to provide approximately the same fiowability asin the above example, in which case anti-caking properties were somewhatbetter than in the example. Soap concentrations of 1% providedsubstantially the same anti-caking properties as in the above example,but somewhat poorer flowabiity although still superior to the untreatedsalt.

All of these samples embodying the combination of soap andsurface-active agent did not form scum or ball up when added to water,and dissolved readily Without stirring.

It will be understood that the above specific examples are for purposesof illustration only and that other amounts and proportions of soap,surface-active agent, and conditioning agent, as Well as other speciesof these agents, may be employed without departing from the spirit ofthe invention. Reference should therefore be had to the appended claimsfor a definition of the limits of the invention.

What is claimed is:

l. A free-flowing, non-caking salt composition consisting essentially ofa normally hygroscopic salt having a water-repellent metal soap adheringto the particles thereof, and a surface-active agent of the groupconsisting of sulphonated amides, substituted ammonium compounds, cyclicquaternary ammonium compounds, polyethylene glycol fatty acid esters,alkyl aryl polyether alcohols and polyalkylene derivatives of hexitolanhydride fatty acid esters, the proportions of soap and surface-activeagent being about 0.05-2.0% and 0.0250.75%, respectively, of the weightof the salt.

2. A free-flowing, non-caking salt composition consisting essentially ofa normally hygroscopic salt having a water-repellent metal soap adheringto the particles thereof, a surface-active agent of the group consistingof sulphonated amides, substituted ammonium compounds, cyclic quaternaryammonium compounds, polyethylene glycol fatty acid esters, alkyl arylpolyether alcohols and polyalkylene derivatives of hexitol anhydridefatty acid esters, and an inert conditioning agent, the proportions ofsoap, surface-active agent and conditioning agent being about 0.05-2.0%,0.025-0.75% and 0.25-5.0%, respectively of the weight of the salt.

3. A free-flowing, non-caking salt composition consisting essentially ofsodium chloride having a water repellent metal soap adhering to theparticles thereof, and a surface-active agent of the group consisting ofsulphonated amides, substituted ammonium compounds, cyclic quaternaryammonium compounds, polyethylene glycol fatty acid esters, alkyl arylpolyether alcohols and polyalkylene derivatives of hexitol anhydridefatty acid esters, the proportions of soap and surface-active agentbeing about 0.05-2.0% and 0.025-0.75%, respectively, of the weight ofsodium chloride.

4. A free-flowing, non-caking salt composition consisting essentially ofsodium chloride having a water-repellent metal soap adhering to theparticles thereof, a surface-active agent of the group consisting ofsulphonated amides, substituted ammonium compounds, cyclic quaternaryammonium compounds, polyethylene glycol fatty acid esters, alkyl arylpolyether alcohols and polyalkylene derivatives of hexitol anhydridefatty acid esters, and an inert conditioning agent, the proportions ofsoap, surface-active agent and conditioning agent being about 0.05-2.0%,0.025-0.75% and 0.25-5.0%, respectively, of the weight of sodiumchloride.

5. A free-flowing, non-caking salt composition as defined in claim 3,wherein the surface-active agent consists of a sulphonated amide in anamount not exceeding about 0.50% of the weight of sodium chloride.

6. A free-flowing, non-caking salt composition as defined in claim 3,wherein the surface-active agent consists of a cyclic quaternaryammonium. compound in an amount not exceeding about 0.20% of the weightof sodium chloride.

7. A free-flowing, non-caking salt composition as defined in claim 3,wherein the surface-active agent consists of a polyalkylene derivativeof a hexitol anhydride fatty acid ester in an amount not exceeding about0.20% of the weight of sodium chloride.

8. A free-flowing, non-caking salt composition as defined in claim 4,wherein the surface-active agent consists of a sulphonated amide in anamount not exceeding about 0.50% of the weight of sodium chloride.

9. A free-flowing, non-caking salt composition as defined in claim 4,wherein the surface-active agent consists of a cyclic quaternaryammonium compound in an amount not exceeding about 0.20% of the weightof sodium chloride.

10. A free-flowing, non-caking salt composition as defined in claim 4,wherein the surfaceactive agent consists of a polyalkylene derivative ofa hexitol anhydride fatty acid ester in an amount not exceeding about0.20% of the weight of sodium chloride.

11. A free-flowing, non-caking salt composition consisting essentiallyof sodium chloride having a water-repellent alkaline-earth metal soapadhering to the particles thereof, and a surfaceactive agent consistingof a polyalkylene derivative of a hexitol anhydride fatty acid ester,the proportions of soap and surface-active agent being about 0.05-2.0%and 0.025-0.20%, respectively, of the Weight of sodium chloride.

12. A free-flowing, non-caking salt composition consisting essentiallyof sodium chloride having a water-repellent alkaline-earth metal soapadhering to the particles thereof, a surface-active agent consisting ofa polyalkylene derivative of a hexitol anhydride fatty acid ester, andan inert conditioning agent, the proportions of soap, surface-activeagent and conditioning agent being about 0.05-2.%, 0.025-0.20% and0.25-5.0%, respectively, of the weight of sodium chloride.

13. A free-flowing, non-caking salt composition consisting essentiallyof sodium chloride having magnesium stearate adhering to the particlesthereof, polyoxyethylene sorbitan monolaurate, and magnesium carbonate,the proportions of magnesium stearate, polyoxyethylene REFERENCES CITEDThe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,234,484: Weinig Mar. 11, 19412,288,409 Lippman et al June 30, 1942 2,422,486 Johnston June 17, 1947OTHER REFERENCES Emulsifying Acaricides. J. Econ. Entomo., 39,

Certificate of Correction Patent No. 2,539,012

January 23, 1951 HORACE W. DIAMOND ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correct1on as follows:

1 Column 1 line 6 for practially read practically column 3, line 4, forthe words as much read a much; column 4, line 64, for 4.5% read 445%;

column 5, line 22, for Hytergren read H ytergen; and that the saidLetters Patent should be read as corrected above, so that the same mayconform to the record of the case in the Patent Oflice.

Signed and sealed this 20th day of March, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,539,012 January 23, 1951 HORACEW. DIAMOND. ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows:

Column 1, line 6, for practially read practically; column 3, line 4, forthe words as much read a much; column 4, line 64, for 4.5% read 4-5%;column 5, line 22, for Hytergren read H ytergen;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the case in the PatentOfiice.

Signed and sealed this 20th day of March, A. D. 1951.

THOMAS F. MURPHY,

Assistant Oommz'ssioner of Patents.

1. A FREE-FLOWING, NON-CAKING SALT COMPOSITION CONSISTING ESSENTIALLY OFA NORMALLY HYGROSCOPIC SALT HAVING A WATER-REPELLENT METAL SOAP ADHERINGTO THE PARTICLES THEREOF, AND A SURFACE-ACTIVE AGENT OF THE GROUPCONSISTING OF SULPHONATED AMIDES, SUBSTITUTED AMMONIUM COMPOUNDS, CYCLICQUATERNARY AMMONIUM COMPOUNDS, POLYETHYLENE GLYCOL FATTY ACID ESTERS,ALKYL ARYL POLYETHER ALCOHOLS AND POLYALKYLENE DERIVATIVES OF HEXITOLANHYDRIDE FATTY ACID ESTERS, THE PROPORTIONS OF SOAP AND SURFACE-ACTIVEAGENT BEING ABOUT 0.05-2.0% AND 0.025-0.75%, RESPECTIVELY, OF THE WEIGHTOF THE SALT.